This invention is concerned with a mould portion for use in moulding molten glass in the manufacture of glass containers. The mould portions used in the manufacture of glass containers have one or more inner surface portions arranged to define a portion of a mould cavity in which molten glass can be moulded. Typically, a mould consists of three portions, two side portions and a bottom plate. The side portions have inner surface portions arranged to define side portions of the cavity of the mould in which molten glass can be moulded and the side portions are movable to allow removal of completed mouldings from the mould cavity. Since the heat absorbed by the mould portions from the molten glass is greater than can be dissipated to the surrounding atmosphere without forced cooling, it is common practice to provide cooling for the mould portions either by blowing air on to the outsides of the mould portions or by passing cooling fluid, usually air, through passages formed in the mould portions. European patent specification No. 0102820 describes an arrangement in which cooling passages in the mould portions are supplied with cooling air from a plenum chamber arranged below the mould portions.
In the manufacture of certain glass containers it is necessary to provide enhanced heat extraction from a portion of the mould portion adjacent the glass-contacting surface thereof. This occurs when the concentration of molten glass is greater in one area of the mould portion than others. For example, where a container having a handle is being moulded, the portion of the mould portion which is encircled by molten glass forming the container and the handle requires enhanced heat extraction. In order to achieve this enhanced heat extraction it is known to provide a rod of a material having a higher thermal conductivity than the remainder of the mould portion, the rod may, for example, be made of copper. This rod extends from the region of the mould portion requiring enhanced heat extraction into a recess in an outer surface of the mould portion. This recess is open to the atmosphere and air is blown into the recess to cool the free end of the rod. Thus, a path of high thermal conductivity is formed between the cooling air entering the recess and the region requiring high heat extraction. The recess may be in the form of a slot cut into the mould portion but the cooling air enters the slot radially of the mould portion and passes the exposed end of the rod in a way which does not remove heat from the rod in a particularly efficient manner.
It is an object of the present invention to provide a mould portion having a rod as mentioned above in which the rod is more efficiently cooled.